Each real time avionic system is architectured and developed to meet performance requirements (notably failure rate and quality of service) in a defined field of use. Each system, connected to other systems, consumes data and services made available by the other systems and produces data of services for the other systems. These interactions are generally set statically during the production of the overall architecture of the “system of systems”, that is to say during the allocation of operational functions to the physical systems. Thus, it is frequent in avionics to have several dozen systems responding to all of the aircraft functions. Typically, the aircraft operations are allocated to the systems according to a logical structure, defined in the standardizing document of the ATA (Air Transport Association). The aircraft architecture therefore breaks down into collaborative avionic systems, each one having a well defined function, and interactions with the other systems in order to provide the expected operational service. The different functions are distributed over several physical computers, as chosen by the aircraft manufacturers, in order to guarantee the performance of the missions.
The onboard systems are qualified, with a demonstrated level of performance, for a given environment. The interactions between systems are defined a priori when the aircraft architecture is generated, and the systems are developed and adjusted to meet the strict interaction requirement.
From the “client-server” point of view, where all of the systems called “client” produce requests to a particular system called “server”, the task of the manufacturers who develop the functions allocated to the “server” is to guarantee that the final performances of the latter will conform with the expected performances and will do so in the field of use defined a priori.
In this field defined a priori, all of the clients are known and well identified; no new client can interact with the system without requalification of the whole of the system.
A major problem is that the addition of a new client to a given system gives rise to a very costly requalification. In fact it is necessary to demonstrate again the maintaining of the operational performance of the whole of the “server” system, even when no new service is expected by the “server” system. This restricts the evolution of aircraft operations.
There is therefore a need to be able to allow the addition of new connections and of new clients to a real time “server” system, guaranteeing for them a quality of service and a response time that does not degrade its performance and does not give rise to software or hardware modifications of the “server”. In this case, the addition of a new client or of a new connection would give rise only to a qualification of the client in question and to a demonstration proving that the performance of the overall system remains in conformity with the required requirements.